Helix type delay detent



Feb. 23, 1960 J. VON NEMETH 2,925,778

HELIX TYPE DELAY DETENT F n E A E= II- INVENTOR. JOS EF VON NEMETH HELIX TYPE DELAY DETENT Josef von Nemeth, Chicago, 111., assignor to Stewart- Warner Corporation, Chicago, Ill., a corporation of Virginia Application March 15, 1957, Serial No. 646,495

2 Claims. (Cl. 10278) My invention relates generally to fuzes and more particularly to an improved setback device, ordetent, to provide at least one means for preventing premature explosion of an artillery projectile, rocket,-'or the like.

In many types of fuzes for projectiles there is provided a priming or relay charge which is aligned with the detonator and main charge only after the projectile has been discharged from the rifle, etc., for a predetermined time interval.

Thus shocks to which the projectile may be subjected in transportation, handling, and loading, even though suificiently severe to cause the detonator to fire, will not cause the main charge of the projectile to explode. This is because the priming or relay charge is not in alignment with the detonator and a port, or passageway, leading to the chamber in which the main charge is located. The final, or at least one step in the arming of the projectile, is accomplished by means responsive to the axial or rotary acceleration of the projectile as it advances through the bore of the rifle or cannon.

In the present invention, the arming mechanism is responsive primarily to the axial acceleration of the projectile and is provided to delay the arming until the projectile being fired is a safe distance beyond the muzzle of the rifle.

It is thus an object to provide an improved setback detonator, the latter being means for delaying the arming of the fuze of a projectile,

in response to its discharge from a rifle.

It is a further object to provide a safe fuze means for projectiles which will prevent accidental explosion of the main charge of a projectile due to shock in transportation, loading, or handling.

Other objects will appear from the following description, reference being had to the accompanying drawings, in which:

Fig. l is a transverse sectional view of a portion of a projectile showing, in enlarged scale, the improved detent or setback means being shown in shutter locking position;

Fig. 2 is a similar view showing the detent in armed position, withdrawn from engagement with the shutter;

Fig. 3 is a fragmentary end elevation showing the.

shutter held in unarmed position by the detent; and

Fig. 4 is a view, similar to Fig. 3, showing the shutter in armed position.

In some types of fuzes, shutters carrying a relay or priming charge are mounted for rotary or angular movement, by the force of a tensioned spring, or by rotary inertia, to bring such charge into alignment, or eiiectrve operative relation, with an impact operated detonator and the main explosive charge. To prevent accidental explosion of the main charge, the shutter is normally locked against such movement by a detent which, either in response to axial or rotary acceleration of the projectile, releases the shutter for movement to 1ts armed position.

The present invention pertains particularly to the provision of improved means for delaying the release of Patented Feb. 23, 1960 the shutter so that it will not be moved to armed positlonin response to shocks incurred in the transportation, handling, dropping, or in ramming the projectile into the chamber of the rifle. Instead, the shutter will be released onlyin response to the application to its detent of a force sustained overan appreciable time interval, of somewhat less duration than the time the projectile is accelerated during its travel through the barrel of the rifle and its projection therefrom.

Thus, although manually set arming devices be incorporated in the projectile, and if these should fail in preventing accidental brisance ofthe detonator, the explosion of the main charge is prevented.

Referring to Figs. 1 and 2 the body 10 of the fuze, which in some instances may be the body of the projectile, is shown in fragmentary section and has a bore 12, counterbore '14, and coaxial recess 16 formed therein. A helically slotted cam 18 is formed in a hollow cylinder 20 which has a flange 21 pressed into the recess 16 and provides a guide for a setback pin 22. This pin normally projects through a'hole 24 in a rotary shutter 26.

Asshown in Fig. 3, the-shutter 26 is provided with a priming or relay charge 28 which is normally out of alignmentwith a passageway 30,. which may or may'not containa booster charge, and which is also out of alignment with the 'brisance discharge passageway 31 of the in alignment with the passageway 30. i

The shutter 26 is mounted for rotation, or oscillation, on a stub shaft 32, fixed with respect to the'housing 10, and is urged to move counterclockwise by a torsion spring 34, one end of which may be anchored to the stub shaft 32 andthe other end of which hooks around a pinor projection 36 on the shutter 26. The counterclockwise movement of the shutter 26 is limited by suitable stop means so that when setback pin is withdrawn from holding position, the shutter swings counterclockwise to the position shown in Fig. 4 in which the priming or boosting charge 28 carried by the shutter 26 is in alignment with the passageways 30 and 31 leading to the main charge and from the detonator respectively, so that the projectile lS1fllllY armed for explosion of the main charge upon brisance of the detonator resulting from impact of the projectile with the target.

In order to provide a safe delay of the complete arming of the projectile by the pivotal movement of the shutter, the setback pin 22 has an enlarged diameter portion 33 which is guided in the sleeve 20 and has a transverse pin 38, one end of which projects into the helical cam slot 18 formed in the sleeve 20. A compression and torsion spring 40 has one end anchored to the reduced diameter (left hand-Figs. l and 2) portion 42 of the setback pin 22, the other end of the spring being anchored to the projectile body or housing 10.

In operation, when the projectile is fired from a rifle, or the rocket is launched, the acceleration thereof (in the present construction mainly axial), causes the setback pin, due to its inertia, to move leftwardly relative to the body 10 (Figs. 1 and 2), because it is assumed that the projectile is discharged from the rifle in a rightward direction, but such arming movement of the setback pin is delayed or retarded by the engagement of the pin 38 with the helical slot 18 and by the fact that the resistance to relative rearward movement of the setback pin 22 increases in accordance with Hookes law. Thus the complete arming of the projectile is substantially delayed.

For example, a setback device of a construction, similar to that shown and described, but not provided with the helix slotted cam sleeve 20 and the pin cooperating therewith, might move .250" and release the shutter, but

in the construction shown (assuming a helix slot of 15 pitch), the pin must travel about four times as far (timewise), before it will move to shutter releasing position. In other words, a sudden shock of a given degree of acceleration, as might be caused by dropping the projectile, would move the setback pin only .062", and would not release the shutter, whereas a sustained acceleration of the projectile, as occurs when the projectile is fired, will cause the spring loaded setback pin to move approximately .250" before the shutter 26 is released and thus assure that the main charge of the projectile will not be prematurely ignited despite failure of the impact operated detonator, or the failure of other arming devices.

While I have shown and described a preferred embodiment of my invention, it will be apparent that numerous variations and modifications thereof may be made without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. In an impact fuse mechanism of the type in which a shutter in an inoperative position thereof prevents alignment of a detonator and a main charge and in which a detent normally engages the shutter to hold the latter in its inoperative position prior to being subjected to set back forces, the combination with the detent of a safety arming device comprising a stationary element defining a helical groove about a predetermined axis, a second element received within the stationary element and connected to the detent, the second element and the detent disposed for reciprocable movement along the axis from a shutter holding position to a shutter release position spaced therefrom, the detent engaging the shutter through a substantial portion of its movement from the holding to the release position, a pin secured to and projecting radially from the second element and extending into the helical groove to cause rotation of the second element and detent relative to the stationary element incident to coaxial movement of the second element and detent, a biasing spring engaging the second element to urge the second element and the detent to the holding position, the spring effective to return the second element and the detent to the holding position subsequent to their movement from the holding position by shock forces of an intensity insufficient to move the second element and detent to the release position.

2. In an impact fuse mechanism of the type in which a shutter in an inoperative position thereof prevents alignment of a detonator and a main charge and in which a detent normally engages the shutter to hold the latter in its inoperative position prior to being subjected to set back forces, the combination with the detent of a safety arming device comprising a stationary annular sleeve defining a helical slot along its periphery, a coaxial piston received Within the sleeve and connected to the detent. the piston and the detent disposed for reciprocable axial movement from a shutter holding position to a shutter release position spaced therefrom, the detent engaging the shutter through a substantial portion of its movement from the holding to the release position, a pin secured to and projecting radially from the piston and extending into the helical groove to cause rotation of the piston and detent relative to the sleeve incident to axial movement of the piston and detent, a biasing spring secured in fixed position at one end thereof and secured at the other end to the piston to urge the piston and the detent axially and rotatively to the holding position, the spring effective to return the piston and the detent to the holding position subsequent to their movement from the holding position by shock forces of an intensity insufficient to move the piston and detent to the release position.

References Cited in the file of this patent UNITED STATES PATENTS 1,053,857 Nordenfelt Feb. 18, 1913 1,316,131 Baldwin Sept. 16, 1919 1,570,620 Crowell Jan. 26, 1926 2,164,115 Lasserre June 27, 1939 2,537,953 Andrews Jan. 16, 1951 2,586,437 Rabinow Feb. 19, 1952 2,595,757 Brandt May 6, 1952 2,712,284 Thomas July 5, 1955 FOREIGN PATENTS 192,509 Germany Sept. 15, 1905 126,351 Great Britain May 15, 1919 720,790 Great Britain Dec. 29, 1954 

